The present invention relates to a synchronous operation control apparatus for rotating a tool and a workpiece in synchronism with each other, and more particularly to a synchronous operation control apparatus for rotating a rotary tool and a workpiece in sychronism with each other by frequency-dividing a pulse train dependent on the number of r.p.m. of the rotary tool based on a predetermined division table, and driving stepping motor for rotating the workpiece based on a frequency-divided output.
There has been employed in the art an apparatus for grinding a number of teeth of a workpiece such as a gear while in mesh with a grinding wheel having helical teeth on an outer peripheral surface thereof. No desired finished gear can be achieved unless the grinding wheel and the gear are rotated in synchronism since the gear teeth would not be ground uniformly by the grinding wheel in the absence of synchronous rotation of the grinding wheel and the gear. To rotate the grinding wheel and the gear in synchronism, the following relation has to be met:
The number of r.p.m. of the grinding wheel.times.the number of teeth of the grinding wheel=the number of r.p.m. of the gear.times. the number of teeth of the gear.
For synchronous operation of the grinding wheel and the gear, it has been conventional practice to incorporate a plurality of speed change gears in a gear drive train and selectively use the gears to rotate the grinding wheel and the gear in synchronism.
With the prior apparatus, however, a number of precision speed change gears are required to thereby render the apparatus large in overall size and expensive. Since the gear changing operation is time-consuming, the downtime of the apparatus is increased or the availability thereof is reduced. Another problem is that since many gears are interposed between the workpiece drive motor and the gear being ground, the accuracy of rotation is lowered due to rotational errors which the individual gears have. It would be possible to employ a numerical control approach in which grinding wheel rotation data and gear rotation data are stored in a memory and the grinding wheel and the gear are rotated on the basis of the stored data. This numerical control arrangement would however be disadvantageous in that the overall apparatus is costly as a motor for rotating the grinding wheel has to be highly accurate.
To cope with the foregoing difficulties, the applicant filed a Japanese Patent Application entitled "Synchronous operation control apparatus in gear grinding machines" on Oct. 3, 1981, the application being laid open on Apr. 8, 1983. According to the earlier application, the apparatus includes a selective pulse output device composed of a central processing unit (CPU), a memory, and a shift register. Selective drive information for driving a workpiece spindle motor is read out of the memory by output pulses generated by a pulse generator coupled coaxially to a grinding wheel spindle motor with a grinding wheel mounted thereon, and the workpiece spindle motor supporting a gear to be ground in mesh with the grinding wheel is energized by the drive information read out of the memory.